Meloidogyne javanica is the most widely spread nematode pest on soybean in South Africa. Only a few registered cultivars have some resistance to this nematode and there is an urgent need for an efficient breeding programme for resistant cultivars of all maturity groups. However, breeding is hampered by laborious screening procedures for selection of resistant lines. The objective of this study was to develop an economically viable molecular marker system for application in selection procedures. Three techniques of marker identification were investigated, i.e. RAPD, RFLP and AFLP analysis. The RAPD technique proved to be applicable in fingerprinting soybean varieties, but was too sensitive for interplant variation to be used as an efficient system for identification of molecular markers linked to nematode resistance. Both RFLP and AFLP screening identified markers linked to gall index variation in a segregating population of 60 F₂ progeny from across between a resistant cultivar, Gazelle, and a highly susceptible variety, Prima. A codominant RFLP marker( B212) was linked significantly to resistance and explained 62% of the variation in gall index. Seven AFLP markers were linked significantly to the resistance trait, of which four were linked in repulsion phase and three in coupling phase. All seven AFLP markers mapped to LG-F on the public soybean molecular map. The QTL for resistance mapped between markers E-ACC/M-CTC2 linked in coupling phase, 8212 and E-AAC/M-CAT1, linked in repulsion phase. These two AFLP markers bracketing the major resistance QTL were successfully converted to SCARs. Marker E-ACC/M-CTC2 was converted to a codominant SCAR marker SOJA6, which acounted for 41% of variation in gall index in the mapping population. Marker E-AAC/M-CAT1 was converted to a dominant SCAR marker (SOJA7) and explained 42% of gall index variation in the mapping population. These two markers mapped approximately 3.8 cM and 2.4 cM respectively from the resistance QTL. This study represents the first report of the development of PCR-based sequence specific markers linked to resistance to M. javanica in soybean. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2000.

A cytokinin habituated soybean callus has been isolated, utilizing the cytokinin soybean bioassay. The habituated callus line was subsequently characterized with a non-habituated callus line in relationship to levels of endogenous growth substances, ultrastructure, nitrogen metabolism and pattern of gene expression. The cytokinin habituated soybean callus contained a higher level of endogenous cytokinin-like activity in comparison to the non-habituated callus. This higher level of cytokinin present is in part due to a lower rate of degradation. The habituated callus tissue produced very low levels of ethylene, while the non-habituated callus produced ethylene at a much higher rate (57 fold higher), than the habituated callus. In contrast to what was found in habituated sugarbeet callus, only low levels of putrescine could be detected in both callus types. The putrescine content of habituated callus tissue was lower than that of non-habituated callus tissue. The ultrastructure of habituated callus cells exhibited several differences to what was observed in the non-habituated callus. Habituated callus cells appeared to have a thinner cell wall than that of the non-habituated callus cells. The cristae of the mitochondria in habituated cells were thicker than that of the non-habituated callus cells, indicating a lower metabolic activity. On day 14 of the growth period the nuclei of habituated callus demonstrated active RNA synthesis as indicated by the presence of several vacuolated nucleoli. Although no significant differences between proline levels of habituated callus and proline levels of non-habituated callus were observed, it was demonstrated that there was a difference in proline metabolism between the habituated and non-habituated calli. Utilizing an inhibitor of OAT, gabaculine, it was shown that in habituated callus tissue proline originated from ornithine during the first 14 days of growth. During the second half of the growth period, which characteristically consists of tissue with low biosynthetic activity, proline originated from glutamate. The production of proline in habituated callus from ornithine also corresponded to a period of high NH₄⁺ content in both callus types, while the production of proline from glutamate corresponded to a period of low NH₄⁺ content in the cells of both callus types. No such correlation was observed in proline metabolism of non-habituated callus. A similar turning point was observed in the activity of OAT of both callus types. Although the specific activity of OAT in both callus types mirrored their changes in RNA concentration, the percentage inhibition of OAT by gabaculine was not significant from day 14 in both callus types. This may indicate a change in the catalyzing properties of OAT in both callus types. It was further demonstrated that the non-habituated callus tissue contained some inhibitor inactivating OAT activity. With the use of gabaculine it was further shown that, in contrast to what was found in other habituated calli, there is no metabolic link between proline metabolism and putrescine synthesis. Both the habituated callus and the non-habituated callus exhibited a high nitrogen influx during the first 14 days of the growth period. The low NH₄⁺ content present in both callus types during the second half of the growth period coincided with higher levels of amino acids present in both callus types. The levels of precursor amino acids (glutamate, aspartate and alanine) did not fluctuate during the growth period, indicating a tight control on amino acid pools. Levels of amino acids further down the path of metabolism did not fluctuate drastically and there appeared to be very little difference between the levels of different amino acids measured in the habituated and nonhabituated calli. Serine was the dominant amino acid in both callus types. Total RNA concentrations of habituated callus were low in comparison to that of the non-habituated callus, except for a striking 12 fold increase on day 14 of the growth period. RNA concentrations of non-habituated callus increased gradually during the growth period and the highest concentration was recorded 21 days after subculturing. Several polypeptides were observed in the habituated callus that were not present in the non-habituated callus, utilizing IEF. Three polypeptides exhibited a change in concentration from day 6 to day 14 of the growth period in both the habituated and nonhabituated callus. These polypeptides appeared to decrease in nonhabituated callus, while they increased in the habituated callus. A complete cDNA library was constructed for both of the habituated and nonhabituated callus lines. Six different clones, that were over expressed in the habituated callus tissue, were isolated via subtractive techniques. One clone was characterized and showed homology to the glutamate/aspartate transport protein, the membrane component, of E. coli. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1998.

Reduced plant population in glyphosate-resistant soybean [Glycine max (L) Merr.] may influence the critical time of herbicide application. Field studies were conducted in 2007 and 2008 at two locations in Kentucky to determine the effect of four weed control programs on soybean seed yield, seed quality, crop canopy, and weed pressure when planted at three densities - 185,000, 309,000, and 432,000 plants ha-1. Plots were treated with glyphosate at either 3 weeks after planting (WAP), 5 WAP, 7 WAP, 3 & 7 WAP, representing common weed control protocols within the state. No differences in seed yield were discovered between plant densities in two of four siteyears. 254,500 plants ha-1 was sufficient for maximum yields in all site-years and was also sufficient to achieve maximum canopy amongst those populations tested in the study. Sequential applications at 3 and 7 WAP provided the highest seed yield, while the 5 WAP and 7 WAP application timings were generally the single applications that allowed for the highest yield and canopy closure, along with the highest visual estimate of weeds controlled. Plant density did not influence the critical period for weed control.

Maximum wheat (Triticum aestivum L.) yields in Zambia were obtained with weekly irrigation at 85% of class A pan evaporation during the whole irrigation interval and split application of urea N of which the initial portion of the fertilizer was either broadcast and incorporated or broadcast after the crop had established itself. This corresponded with maximum utilization of fertilizer N. The proportion of N derived from fertilizer was independent of fertilizer placement at various water regimes and N utilization was primarily a function of water availability. / Two nonnodulating soybean (Glycine max L.) cultivars, Clark RJ1 and N77, or in their absence Pearl millet (Panicum glaucum L.) were judged to be appropriate reference crops for estimating N$ sb2$ fixation by soybeans using $ sp{15}{ rm N}$ isotope dilution techniques. A local soybean cultivar, Magoye, was rated highest among three cultivars tested for its ability to support N$ sb2$ fixation by Bradyrhizobium japonicum and contributed biologically fixed N$ sb2$ to a subsequent wheat crop.

Thesis (M.S.)--Mississippi State University. Department of Plant and Soil Sciences. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 160-168). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 160-168). Also available on the Internet.

Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is the most devastating pathogen of soybeans, Glycine max (L.) Merr., causing over $1 billion in yield losses annually in the United States alone. Currently, planting of genetically resistant cultivars is the most commonly employed management strategy. Due to an overuse of genetic resistance derived from the soybean variety ‘PI 88788’, many populations of soybean cyst nematodes are becoming virulent on previously resistant cultivars, urging the understanding and discovery of alternative mechanisms of SCN resistance. In this study, we will delve into the history and epidemiology of Heterodera glycines, learn about the molecular etiology underlying SCN pathogenesis, begin to understand the mechanism of resistance by Peking-type soybeans, and look to discover a novel mechanism of resistance by establishment of a mutagenized population of the soybean variety ‘PI 567516C’.

Made available in DSpace on 2014-06-11T19:31:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-15Bitstream added on 2014-06-13T20:42:12Z : No. of bitstreams: 1 bovolenta_fc_me_botfca.pdf: 865517 bytes, checksum: 9e87bc5db77a17bb3fd0db1388332215 (MD5) / O presente trabalho objetivou analisar o fluxo energético considerando as rotas atualmente existentes para o escoamento de soja da região centro-oeste do Brasil, mais precisamente, do município de Rio Verde (GO) até o porto de Santos (SP), visto que, é um grande pólo exportador de granéis sólidos. Foram selecionadas duas rotas para a análise, uma contemplando a multimodalidade, ou seja, os modais rodoviário, ferroviário e hidroviário, e outra, uma única modalidade, o modal rodoviário. A conversão dos fatores físicos e operacionais envolvidos nos sistemas logísticos, multimodal e unimodal de transportes estudados se deu por meio de coeficientes energéticos levantados junto à literatura. Os resultados obtidos indicaram, pela rota 1 multimodal, com gasto energético específico maior o modal rodoviário (0,50 MJ.km-1.t-1), seguido pelo modal ferroviário (0,42 MJ.km-1.t-1) e, em terceiro, o modal hidroviário (0,22 MJ.km-1.t-1). Pela rota 2 unimodal rodoviário, o resultado indicou 0,50 MJ.km-1.t-1. Nas participações de energia apresentadas, comparando as rotas 1 e 2, a que apresentou maior gasto energético específico foi a rota 2 (0,50 MJ.km-1.t-1), seguida pela rota 1 (0,34 MJ.km-1.t-1). / The present work objectified to currently analyze the energy flow considering the existing routes for the draining of soy of the region center-west of Brazil, more necessarily, of the city of Rio Verde (GO) until the port of Santos (SP), since, it is a great exporting polar region of solid granaries. Two routes for the analysis had been selected, one contemplating the multimodality, that is, modal the road, together railroad worker and water road, and another one, an only modality, the modal road. The conversion of involved the physical and operational factors in the systems logistic, multimodal and unimodal of studied transports if gave by means of raised energy coefficients next to literature. The gotten results had indicated, for multimodal route 1, with energy expense specific greater the modal road (0,50 MJ.km-1.t-1), followed for modal railroad worker (0,42 MJ.km-1.t-1) e, in third, the modal water road (0,22 MJ.km-1.t-1). For route 2 road unimodal, the result indicated 0,50 MJ.km-1.t-1. In the presented participation of energy, comparing routes 1 and 2, the one that specific energy expense presented greater it was route 2 (0,50 MJ.km-1.t-1), followed for route 1 (0,34 MJ.km-1.t-1).

Orientador: Marco Antonio Martim Biaggioni / Banca: Osmar de Carvalho Bueno / Banca: Luís Fernando Nicolosi Bravim / Resumo: O presente trabalho objetivou analisar o fluxo energético considerando as rotas atualmente existentes para o escoamento de soja da região centro-oeste do Brasil, mais precisamente, do município de Rio Verde (GO) até o porto de Santos (SP), visto que, é um grande pólo exportador de granéis sólidos. Foram selecionadas duas rotas para a análise, uma contemplando a multimodalidade, ou seja, os modais rodoviário, ferroviário e hidroviário, e outra, uma única modalidade, o modal rodoviário. A conversão dos fatores físicos e operacionais envolvidos nos sistemas logísticos, multimodal e unimodal de transportes estudados se deu por meio de coeficientes energéticos levantados junto à literatura. Os resultados obtidos indicaram, pela rota 1 multimodal, com gasto energético específico maior o modal rodoviário (0,50 MJ.km-1.t-1), seguido pelo modal ferroviário (0,42 MJ.km-1.t-1) e, em terceiro, o modal hidroviário (0,22 MJ.km-1.t-1). Pela rota 2 unimodal rodoviário, o resultado indicou 0,50 MJ.km-1.t-1. Nas participações de energia apresentadas, comparando as rotas 1 e 2, a que apresentou maior gasto energético específico foi a rota 2 (0,50 MJ.km-1.t-1), seguida pela rota 1 (0,34 MJ.km-1.t-1). / Abstract: The present work objectified to currently analyze the energy flow considering the existing routes for the draining of soy of the region center-west of Brazil, more necessarily, of the city of Rio Verde (GO) until the port of Santos (SP), since, it is a great exporting polar region of solid granaries. Two routes for the analysis had been selected, one contemplating the multimodality, that is, modal the road, together railroad worker and water road, and another one, an only modality, the modal road. The conversion of involved the physical and operational factors in the systems logistic, multimodal and unimodal of studied transports if gave by means of raised energy coefficients next to literature. The gotten results had indicated, for multimodal route 1, with energy expense specific greater the modal road (0,50 MJ.km-1.t-1), followed for modal railroad worker (0,42 MJ.km-1.t-1) e, in third, the modal water road (0,22 MJ.km-1.t-1). For route 2 road unimodal, the result indicated 0,50 MJ.km-1.t-1. In the presented participation of energy, comparing routes 1 and 2, the one that specific energy expense presented greater it was route 2 (0,50 MJ.km-1.t-1), followed for route 1 (0,34 MJ.km-1.t-1). / Mestre